There is always a need to improve the quality and performance of motor gasoline. Particular beneficial improvements desired include, e.g. lower cost, increased fuel economy, higher octane rating (anti-knock quality), and decreased exhaust emissions.
For instance, the use of absolute ethanol (200 proof ethanol) as a fuel component and octane improver in blends with gasoline is well known in the art, as seen e.g. by commercial "gasohol" which consists essentially or a 90/10 volume percent blend of gasoline and absolute ethanol. However, fuel composition blends of gasoline and ethanol are very sensitive to water contamination and in general have heretofore exhibited a very limited phase stability tolerance for water, particularly at low temperatures of about 0.degree. C. and below. Moreover, it is well known that such phase separation into a gasoline-rich phase and an ethanol-water phase can result and lead to severe internal combustion engine operation problems, e.g. stalling, fuel line freezing, and the like. Such phase separation probability is believed to be the primary reason that the only commercially available gasoline-ethanol fuel compositions are those prepared using absolute ethanol instead of hydrous ethanol. Moreover while a gasoline-ethanol fuel composition producer may take precautions to avoid phase separation by excluding water during the production, storage and distribution of such fuel compositions, there is little, if anything, that can be done by the producer to avoid water contamination during the retail marketing and/or individual use of such fuel compositions.
Consequently, the discovery of gasoline-ethanol fuel compositions having improved phase stability tolerances to water over a wide temperature range such as those that would have cloud points of 0.degree. C. or below, while at the same time having octane ratings above that of the gasoline employed, would obviously be of no small importance to the state of the art. Such superior phase-stable fuel compositions would permit the use of hydrous ethanol instead of absolute ethanol in the production of said fuel compositions and such an accomplishment in itself would lead to a wide variety of obvious benefits, not the least of which is the fact that the production of hydrous ethanol is less energy-intensive than the production of absolute ethanol and thus is far easier and much less expensive to product.
Indeed, the search for phase-stable gasoline-hydrous ethanol fuel compositions suitable for use in internal combustion engines has been a long and constant one in the art as seen e.g. by the following prior art.
U.S. Pat. Nos. 4,207,076 and 4,207,077 are directed to fuel compositions consisting of a major amount of gasoline, a minor amount of 190 proof ethanol and an alkyl-t-butyl ether as a cosolvent.
U.S. Pat. Nos. 3,822,119 is directed to an anti-pollution, anti-knock fuel composition comprising a mixture of gasoline, water and an alcohol containing from 4 to 8 carbon atoms. Said patent further discloses that additionally simple alcohols such as methanol, ethyl alcohol, n-propyl or isopropyl can be employed as a solubilizing agent.
A technical paper entitled "Use of 95% Ethanol in Mixtures With Gasoline" by A. Schmidt, in Comm. Eur. Communities [Rep." EUR June 1981, EUR 7091, Energy Biomass, Conf., 1st pp. 928-933 (Eng.) is directed to gasoline-95% ethanol mixtures and their phase stability at low temperatures as well as to the use of propanols or butanols as co-solvents.
Hydrocarbon Processing, May, 1979, pp. 127 to 138, contains an article "Alcohols as Motor Fuels?" by J. Keller which discusses gasoline blends of methanol and ethanol along with higher alcohols as a cosolvent to improve water tolerance (page 133).
U.S. Pat. No. 2,104,021 is directed to fuel compositions for internal combustion engines comprising a non-benzenoid hydrocarbon composition, water, ethanol, and as stabilizing agents therefore, a saturated aliphatic ether and a higher alcohol, in a quantity sufficient to maintain a homogeneous mixture or blend at sub-zero temperatures.
However, none of the above prior art references is seen to disclose an example of a single specific gasoline-ethanol fuel composition as encompassed by the invention of this application, nor are said references seen to render obvious the unique combination of phase stability and high octane properties possessed by the fuel compositions of this invention.